1. Field of the Invention
This invention relates to an apparatus for separating solutes from liquids by a reverse osmosis process, and in particular it concerns an apparatus and the method of manufacturing same in which there is contained in a pressure vessel a tubular separating element or cartridge comprising a semipermeable film envelope and a corrugated spacer wound around a pipe for collecting the liquid that permeates through the film. The separating element defines a continuous uninterrupted channel through which can be passed the liquid to be treated, as well as objects to clean the film.
2. Description of the Prior Art
Heretofore, difficulties were encountered in processes for the separation and treatment of liquids in the reverse osmosis process because the semipermeable membrane surface becomes soiled and its permeability efficiency is reduced. It is well known that such soiled surfaces can be effectively cleaned by sponges and like cleaning members.
The type of spearator for which such a cleaning method can be employed is called a tubular-type separator and it has semipermeable films on the inner surfaces of outer tubes. These films can be scrubbed clean when sponge balls are pushed therethrough in a liquid stream. However, in this type of separator, the surface area of the film, per unit volume of the separator (sometimes called the filling efficiency), is low. Also one pressure resistant pipe is necessary for each tubular film. Further, it is necessary in this type of separator to connect several or more sections of tubular films with one another in series by using return conduit bends in order to obtain a desired total film surface area in the apparatus. This increases the number of parts required for the apparatus and is economically disadvantageous.
Another type of separator, called the spirally wound-type, is constructed by inserting a spacer between a flat semipermeable membrane film and winding the spacer and film together in a spiral fashion. A spirally wound-type separator cannot be cleaned by sponge balls or the like, but it is excellent in the filling efficiency per unit volume. Thus, the second type of separator is mainly used in industry.
The present invention provides a separator which retains the advantages, but eliminates the defects, of both of the above-mentioned respective types of separation apparatuses.